How to record audio as mp3 file by using AvAudiorecorder in iOS

Question

How to record audio as an mp3 file by using AvAudiorecorder?.I m using the following code for the recorder setting

recordSetting =  [NSDictionary dictionaryWithObjectsAndKeys:
                  [NSNumber numberWithInt:AVAudioQualityMin],AVEncoderAudioQualityKey,
                  [NSNumber numberWithInt:16], 
                   AVEncoderBitRateKey,
                   [NSNumber numberWithInt: 2], 
                   AVNumberOfChannelsKey,
                   [NSNumber numberWithFloat:44100.0], 
                   AVSampleRateKey,nil];